Iniesta and his family are the third-tier club's majority shareholders and he said they were doing everything they could to stop Albacete folding but needed more outside investment.
"Using this letter I would like to encourage everyone who has been connected with this club, former players, fans, companies and institutions to take part in the third phase of the capital increase so that we can safeguard our historic club," he wrote.
"The country is going through a very difficult economic situation and we will only resolve this situation if all of us who can make an effort."
Albacete, who have had a couple of stints in Spain's top flight, are the latest club to suffer financially as the economic crisis gripping Spain dents revenue from ticket sales and sponsorship.
- Sports & Recreation